It is the specific aim of this research proposal to study the antigenicity of the melanosome and its relation to autoimmunity against pigment cells with the ultimate goal of making possible specific immunological tests for the diagnosis of malignant metastatic melanoma. Melanosomes from B-16 mouse melanoma will be purified by differential centrifugation. Antigens will be prepared from purified melanosomes by using intact particles as well as soluble and insoluble subfractions. Antibody will be prepared in rabbits as well as mice. Agglutination, gel diffusion and delayed hypersensitivity tests will be used to study the specificity of the host immune responses. Preliminary work in the author's laboratory has already demonstrated that mouse melanosomes are antigenic in rabbits and that meaningful qualitative and quantitative measurements with respect to the nature of melanosome antigens can be made using the proposed methodology. The medical literature indicates that human melanoma patients mount immune responses to their tumors which include cellular and humoral factors against both cell-surface and internal cytoplasmic antigens of melanoma cells. There are also several non-malignant pigment cell disorders that strongly suggest autoimmune factors. This proposal suggests that the B-16 mouse melanoma will be a very useful animal model system in which to study the nature of immunity to pigment cell antigens. We will look for antigen(s) present in all pigment cells and only in pigment cells with a view to their potential use as diagnostic reagents for the progress of malignant melanoma.